Will be better when Keith“s plugin for OpenSeaMaps allows access to ALL areas.

Tore

Will this eventually show soundings? With my 18-inch draft soundings are less important to me than they used to be when I sailed deeper draft boats, but I'm still used to seeing them and like to have that information.

Well,that has always been the BIG problem with OpenSeaMap,navigation marks can,laboriously be added over time by the users,but soundings is another matter.

Unless there is a world-wide database of soundings we can gain access to,there is only one other way using overlays from all charts which can be displayed in opencpn using Paul“s GE2KAP. In difficult areas,you can also get some idea of draughts creating .kap charts purely from Google Earth.

Tore

__________________"And all I ask is a tall ship and a star to steer her by."

I couple of years ago I tried to convince some guy at Openseamap, that, if we all collect soundings (via NMEA) when we sail, upload the data to a central database, e.g. hosted with the openseamap-project, then eventually we will have a global/regional sounding database to be visualized on charts.

I'm sure that some software to validate the soundings and then make the soundings visible on Openseamap-charts (and S57 charts?) is possible to make. I'm also sure that some open source-software in the GIS-world would exist somewhere, but that's just a guess. The challenge is collecting and storing the soundings.

But why would that be different from all the data collected in the Openstreetmap-project? Except for the storage format, maybe?

Does anybody else but me see the idea? Is it impossibe? I know it's 'big data', but it could be 'regionalized' to us poor europeans, who do not have a NOAA organization offering free charts.

Actually a guy (Fiskekortet.dk Forside) started collecting soundings from a number of fellow small fishing boats and doing exactly what I'm trying to suggest. His fishing charts are quite impressive, with different colourings for various depths. He seems to make it a business idea now, so he's not an open source guy.

The collection, storage, post-processing and display of depth data is a very big project. OpenSeaMap has been looking at this for some time now, but are unlikely to be able to add this feature any time soon. Another project - teamsurv.eu - has done some work on crowd-sourced depth data, but have so far only covered a few small areas.

This is a very complex process. Depth sounder and GPS data has to be corrected for actual tidal conditions at the time of measurement. This requires access to historical data from a nearby tide gauge. Also important is the relative vertical and horizontal positions of the depth sounder and GPSantenna, so each vessel gathering this data must include this calibration data with its upload. Other corrections, such as sea temperature, GPS time lag, etc. also have to be factored in.

As an experiment I have created my first OpenSeaMap with soundings from CM93,keeping the original sea mark information.

1.Downloaded an OpenSeaMap in .kap format
2.Installed it in my OpenCPN map directory and re-built the database.
3.Selected the required map scale and set “Grid on“
4.Screenshot of the displayed OpenSeaMap in full page mode. “Grid on“
5.“Cleared all“ in the Mariner“s standard in Vector Charts section of OpenCPN
6.Screenshot of the soundings in the CM93 display. “Grid on“
7.Loaded up the OpenSeaMap page in GIMP2
8.Loaded up the CM93 soundings page as overlay in GIMP2 and made background transparent. Adjusted the overlay to fit the grid lines of both maps.
9. Reduced colours to 127 and exported as .png
10.Loaded up in MapCalII and calibrated the four corners nearest identifiable points
selected from the original (unchanged) CM93 map in OpenCPN. Saved.
11. Loaded up in GE2KAP and converted final chart to .kap.

OK, quite a few steps but it works as you see from the attached example.

Tore

Attached Thumbnails

__________________"And all I ask is a tall ship and a star to steer her by."

The collection, storage, post-processing and display of depth data is a very big project. OpenSeaMap has been looking at this for some time now, but are unlikely to be able to add this feature any time soon. Another project - teamsurv.eu - has done some work on crowd-sourced depth data, but have so far only covered a few small areas.

This is a very complex process. Depth sounder and GPS data has to be corrected for actual tidal conditions at the time of measurement. This requires access to historical data from a nearby tide gauge. Also important is the relative vertical and horizontal positions of the depth sounder and GPS antenna, so each vessel gathering this data must include this calibration data with its upload. Other corrections, such as sea temperature, GPS time lag, etc. also have to be factored in.

Thanks indeed for your information. I did not know the teamsurv.eu-project, thanks. I quite understand the challenge, but unfortunately I don't know the decisionprocesses or the criteria for selecting projects at Openseamap. Could be money of course :-) . But I think the openseamap-project is useless without soundings.

The idea could be to make projects available for local initiatives, - having a number of local sounding collectors collect data on a small specific sea territory and then using the resulting data to verify against authorized seamap-sources and also to indicate directions for next steps. That would make useful data to locals and useful experience to get further on.

Nobody would require the sounding-data to be authorized navigational aids, of course, but he validity of crowd-sourcing could indeed challenge the existing (typically governmental) sources of soundings.

Crowd-sourcing could indeed improve the quality of soundings targeted against sailors like in this forum. Detailed soundings on sea-areas not used by commercial traffic, but used by sailing-boats, hobby fishermen etc..

-I am quite sure the soundings are covered by copyright. There is no reason they should not be covered by the copyright for the chart itself

-Making large scale soundings is illegal in some countries. In Sweden, I believe it is illegal to do surveys/sea charts without authorization by the authorities. (I have not checked this the last few years...but it used to be illegal...)

I know that the Hydrographica company that makes independent large scale map of areas of interest for the boating community in Sweden only got right to publish depts more shallow than 6 m. (or maybe 5 m ...). This is of course ok for us, very few of us amateur boaters have a draft exceding 5 meter...

Doing some soundings for personal use might be ok, but to survey and publish on large scale might be both violating intelectual property rights and get you in trouble with the defence forces/Navy in some countries.

Before starting a large scale effort I think this needs attention.

I do however think the idea is great. There are many areas of interest for amateur boaters that are poorly charted. If it existed an easy to install application that could be used to collect and send data to a central depository I guess it should be possible to filter out the correct information if there is just enough data.

But, it is not only the problem of tide.

In Sweden my experience is that in shallow waters the pulp/algae that grow in shallow bays during the summer disturbs the reading. It was quite common that I got readings more shallow than my draft. I used this as an indicator to move with caution, it did not stop me. (Passed tense since I don't live in Sweden anymore...)

Wouldn't it be nice if OpenCPN could include depth soundings in its track files so that users who wanted to contribute to such a data collection effort could simply upload track files? The track files would need to include latitude, longitude, date, time, and depth for each sample point. The collecting site would need to ask uploaders for the depth offset appropriate for their boat. In my case, for example, depth soundings give the depth under the keel so my soundings would have to be increased by 18" to give depth from the surface.

The collecting site could use the location, date, and time to ascertain the state of the tide when the sample was collected. As multiple samples are collected from any location the depth information could be refined with common statistical tools.

More than a year later and it seems like it has, sad to say. I would love to see an OpenCPN plugin for OSM files. Unfortunately, I have neither the time, nor the programming ability, to make this happen.

could you be more specific about the intended integration? Should it create charts, or maybe just display items on top of existing charts? I looked at this plugin briefly and it appeared to not really do anything, so I could not figure out the intended purpose.